1. Field of the Invention
One disclosed aspect of the embodiments relates to a photoelectric conversion device which includes a plurality of semiconductor substrates.
2. Description of the Related Art
In a related art photoelectric conversion device, a photoelectric conversion unit including a plurality of photoelectric conversion elements, a signal processing unit for processing an electrical signal from the photoelectric conversion unit, and a control unit for controlling the photoelectric conversion unit and the signal processing unit are monolithically mounted on a single semiconductor substrate. It has been demanded to increase an area of the photoelectric conversion unit, to reduce the area of the photoelectric conversion device and to achieve higher signal processing capability. In Japanese Patent Laid-Open No. 2011-159958, it is discussed to stack a plurality of semiconductor substrates, to provide a photoelectric conversion unit in one of the semiconductor substrates and provide a signal processing unit in the other of the semiconductor substrate.
Since the signal processing unit is driven at higher speed (at higher frequency) than the photoelectric conversion unit, the power consumed in the signal processing unit is larger than that consumed in the photoelectric conversion unit. Generated heat becomes greater in proportion to the consumed power. If a plurality of semiconductor substrates are stacked, since these semiconductor substrates are positioned close to each other, an influence of generation of heat of the signal processing unit becomes significant as compared with a case in which the photoelectric conversion unit and the signal processing unit are mounted monolithically on a single semiconductor substrate.